The disclosure relates generally to apparatus and methods that perform frame rate conversion and more particularly to methods and apparatus that perform frame rate conversions using source frames from a decoder.
Video display systems such as high definition televisions, laptop computers, handheld devices, or any other devices, process encoded video streams whether encoded in an MPEG format or any other suitable format to produce decoded video frames. As used herein, the term frame will be used although it will be understood that fields are also covered by this term. As decoders decode streams of video information, they may have difficulty in outputting frames that have a rate desired by a display or display subsystem. If a decoder does not properly decode a frame (e.g., CPU is too busy to decode or control decoder properly), a “dropped” frame condition occurs or a corrupted frame is generated. The decoder then typically repeats a previously decoded frame as the dropped frame. This is sometimes referred to as a “repeated last frame” approach. This can be unsatisfactory, however, because the smoothness of any motion in the scene can be disrupted.
Frame rate conversion is the process of converting decoded source frames that are being output by a decoder, for example, at a 24 Hz rate, to different rate of frames, for example, at a 60 Hz rate. The frame rate conversion process is done as part of a post-decode operation after the frames have been decoded by a decoder. Frame rate conversion in this example requires a differing number of frames to be generated from the source frames and multiple source frames are used to generate each frame rate converted frame. However, if the decoder provides a repeated last frame because the prior frame was dropped or if the decoder outputs a corrupted frame, the resulting video can have poor quality (e.g., poor apparent motion if motion is in the scene). The repeated last frame approach can result in the disturbance in cadence caused by dropped frames.
Accordingly, it would be desirable to have an improved method and apparatus that better handle dropped frame conditions or corrupted frame conditions in a frame rate conversion process.